Brother Cadfael's Penance (Brother Cadfael Mysteries)

While Cadfael has bent Abbey rules, he has never broken his monastic vows--until now. Word has come to Shrewsbury of a treacherous act that has left 30 of Maud's knights imprisoned. All have been ransomed except Cadfael's secret son, Olivier. Conceived in Cadfael's soldiering youth and unaware of his father's identity, Olivier will die if he is not freed.